This invention refers to modifications to the current two-stroke cycle internal combustion engines, those which execute one full cycle for each rotation of the crankshaft, with the difference that it uses shorter pistons and the fuel does not enter the engine crankcase. For this purpose, it is proposed: a) To use piston rods solid with the pistons, similar to those used by engines using double acting pistons (such as steam engines); b) to install rotary valves in the transfer and exhaust ports; c) operate one-way flow valves directly by pressure differential; d) to install an auxiliary mechanism to pump lubricant to the piston rings.